Various kinds of chelating agents, ion exchange materials, alkalizers, and dispersants have been known to be used for builders to be blended in detergents. Since the phosphate-based chelating agents having tripolyphosphates as a main component thereof have good water solubility and washing power, they are preferred.
In recent years, the use of tripolyphosphates has decreased, since they can cause eutrophication in closed freshwater areas such as lakes and marshes. Instead, crystalline aluminosilicates (zeolites), typically those disclosed in Japanese Patent Laid-Open No. 50-12381, have been commonly used. In a detergent blend using the above zeolite, the standard amount of dosage for the detergent in Japan is generally about 40 g/30 L. Also, the powdery detergents available at that time had low bulk density of from 0.20 to 0.45 g/ml from the viewpoint of solubility in cold water. As a result, the standard volumetric amount of dosage was about from 90 to 200 ml/30 L, which were extremely inconvenient for handling in distribution, at stores and homes.
Therefore, an intense investigation has been made to produce compact detergents. For instance, Japanese Patent Laid-Open Nos. 62-167396, 62-167399, and 62-253699 disclose remarkable decrease in the amount of crystalline inorganic salts such as sodium sulfate used as powdery aids conventionally contained in detergents. In addition, Japanese Patent Laid-Open Nos. 61-69897, 61-69899, 61-69900, and 5-209200 disclose that by increasing the bulk density of the detergents, to thereby have a bulk density of from 0.60 to 1.00 g/ml, only a standard amount of dosage of 25 to 30 g/30 L is required, thereby making the detergents compact to have standard volumetric amount of dosage of from 25 to 50 ml/30 L.
However, in conventional detergents, a large amount of surfactants had to be blended in the detergent compositions because the mainstream idea was to make the oily components in dirt soluble by surfactants. Specifically, sebum dirt originated by human bodies, which is the most typical dirt adhered to clothes, most likely to be observed on collars and sleeves, is an example. The sebum dirt contains oily components, such as free fatty acids and glycerides, with a high content of not less than 70% (Ichiro KASHIWA et al., "Yukagaku," 19, 1095 (1969)). The oily components lock carbon and dirt in dust and peeled keratin, so that the resulting substance is observed as dirt. In order to wash off the sebum dirt, conventionally, detergents are designed based on a washing mechanism mainly by making these oily components soluble with micelle of surfactants, thereby detaching carbon, dirt, and keratin from clothes. This technical idea has been widely established among those of ordinary skill in the art, and even when the conventional detergents are shifted to compact detergents, substantially no changes took place in the surfactant concentration in the washing liquid. This fact is described in "Dictionary for Detergents and Washing," Haruhiko OKUYAMA et al., p. 428, 1990, First Edition, Asakura Publishing Company Limited, which shows that there are substantially no changes in concentrations in the washing liquid for components other than sodium sulfate.
Based on these washing principles, the surfactant concentration in the washing liquid has to be made high in order to achieve high washing power, so that a large amount of surfactants has to be blended in the detergent composition. Therefore, a drastic reduction in the standard amount of dosage of the detergents was actually difficult. In addition, the presently known production method substantially enables to increase the bulk density to a level of about at most 1.00 g/ml. Therefore, a further reduction in the standard volumetric amount was deemed to be technically extremely difficult problem.
On the other hand, crystalline silicates having particular structure disclosed in Japanese Patent Laid-Open Nos. 5-184946 and 60-74595 shows not only good ion exchange capacity and actions of alkalizers (alkaline capacity). Therefore, possibility of more compact detergents has been investigated because both of the functions of two different components, including metal ion capturing agents, such as zeolites, and alkalizers, such as sodium carbonate, can be satisfied with the above crystalline silicates alone.
For instance, Japanese Patent Laid-Open No. 6-116588 is concerned with a detergent composition containing a crystalline silicate. In Examples of this publication disclosing a more compact detergent, even in a case where the amount of the detergent composition at washing is reduced by 25%, the detergent composition has a washing power substantially the same as conventional detergent compositions. However, since the composition was formulated based on the conventional washing principle, the surfactant concentration was high, and the alkaline capacity and the ion exchange capacity were ascribed solely to the crystalline silicates contained therein. In this case, the functions of the crystalline silicates as alkalizers precede their functions as metal ion capturing agents, so that the washing power of the detergent composition was not always satisfactory. Therefore, if the amount of dosage of the detergent composition were reduced, a good washing power could not maintained.
A number of patent applications have been filed concerning the crystalline silicates disclosed in Japanese Patent Laid-Open NO. 60-74595. Japanese Patent Unexamined Publication No. 6-502199 discloses a detergent comprising a layered crystalline silicate, a zeolite, and a polycarboxylate in particular proportions, to thereby provide a detergent free from providing film layer formation on fibers and having excellent washing power and bleaching agent stability. However, under the blending conditions given in this publication, when the amount of the detergents added was reduced at washing, the alkaline capacity is not sufficient because the amount of silicate in the builder composition is small, thereby making it impossible to maintain good washing power. Also, this publication never teaches the technical idea that an excellent washing power is exhibited in a small amount of dosage of detergents.
The technical idea that an excellent washing power is exhibited in a small amount of dosage of detergents as in the present invention cannot be found for detergents containing crystalline silicates disclosed in Japanese Patent Unexamined Publication 6-500141, Japanese Patent Laid-Open Nos 2-178398 and 2-178399. Rather, in the case where the amounts of the detergent compositions shown in each of Examples are reduced, the washing power is lowered.
Further, U.S. Pat. No. 4,303,556 and EP-A-0550048 disclose detergent compositions comprising surfactants, aluminosilicates, and alkali metal silicates. However, these publications do not disclose that the detergent compositions show high washing power even when the surfactant concentration is low.